Flexible optical circuit, cassettes, and methods

ABSTRACT

A fiber optic cassette includes a body defining a front and an opposite rear. A cable entry location, such as a multi-fiber connector, is defined on the body for a cable to enter the cassette, wherein a plurality of optical fibers from the cable extend into the cassette and form terminations at one or more single or multi-fiber connectors adjacent the front of the body. A flexible substrate is positioned between the cable entry location and the connectors adjacent the front of the body, the flexible substrate rigidly supporting the plurality of optical fibers. Each of the connectors adjacent the front of the body includes a ferrule. Dark fibers can be provided if not all fiber locations are used in the multi-fiber connectors. Multiple flexible substrates can be used with one or more multi-fiber connectors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/980,789, filed Dec. 28, 2015, which is a continuation of U.S.application Ser. No. 14/045,509, filed Oct. 3, 2013, now U.S. Pat. No.9,223,094, which claims the benefit of U.S. Provisional Application No.61/710,519, filed Oct. 5, 2012, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

As demand for telecommunications increases, fiber optic networks arebeing extended in more and more areas. Management of the cables, ease ofinstallation, and case of accessibility for later management areimportant concerns. As a result, there is a need for fiber optic deviceswhich address these and other concerns.

SUMMARY

An aspect of the present disclosure relates to fiber optic devices inthe form of fiber optic cassettes that include at least one connectorthat provides a signal entry location and at least one connector thatprovides a signal exit location and a flexible fiber optical circuitthereinbetween for relaying the signal from the entry location to theexit location. The cassette can have many forms. The cassette isoptional, if desired to use the flexible fiber optical circuit in otherequipment.

Another aspect of the present disclosure relates to a fiber opticcassette including a body defining a front and an opposite rear. A cableentry location is defined on the body for a cable to enter the cassette,wherein a plurality of optical fibers from the cable extend into thecassette and form terminations at one or more connectors adjacent thefront of the body. A flexible substrate is positioned between the cableentry location and the connector adjacent the front of the body, theflexible substrate rigidly supporting the plurality of optical fibers.Each connector adjacent the front of the body includes a ferrule. Aconnector at the rear also includes a ferrule. Single fiber connectorsor multi-fiber connectors can be used. Also, various combinations of thefront, the rear, the sides, the top and the bottom of the cassette canbe used for the connectors, as desired. For example, only front accessis possible.

According to another aspect of the present disclosure, a method ofassembling a fiber optic cassette includes providing a body, mounting amulti-fiber connector terminated to a multi-fiber cable to the body,fixedly supporting the plurality of the optical fibers extending fromthe multi-fiber connector on a flexible substrate, and terminating onlya portion of the plurality of optical fibers supported by the flexiblesubstrate with another multi-fiber connector that includes a ferrule.Dark fibers on the flexible substrate fill any unused holes in theferrules of the multi-fiber connectors.

According to another aspect of the present disclosure, a flexibleoptical circuit includes a flexible substrate and a plurality of opticalfibers physically supported by the flexible substrate, wherein a firstend of each of the optical fibers is terminated to a multi-fiberconnector that is coupled to the flexible substrate and a second end ofeach of the optical fibers is terminated to another fiber opticconnector that is coupled to the flexible substrate, the other fiberoptic connector including a ferrule. Dark fibers can be used. Fibers canbe separated and connected to different connectors. Multiple layers ofthe flexible optical circuit can be provided, as desired.

One aspect of the present invention includes using multi-fiberconnectors to connect to other multi-fiber connectors.

Another aspect of the present invention includes using multi-fiberconnectors connected to a flexible foil wherein some of the fibers inthe connectors are inactive, or dark. The flexible foil includes fiberstubs integral with the flexible foil which fill the multi-fiberconnectors with the desired inactive fibers.

Another aspect of the present invention relates to utilizing multi-foillayers in combination with a multi-fiber connector. A further aspect ofthe present invention includes using multilayers of flexible foils andconnectors with multiple rows of fibers. In some cases, the fibers fromdifferent layers can be mixed with different rows of the connectors.

According to another aspect of the present invention, some fibers on theflexible foils can be passed through to other connectors and otherfibers can be looped back to the same connector or another connector fortransfer of signal to another connector.

According to another aspect of the present invention, the flexible foilscan be used to manage the optical fibers wherein certain of theconnectors of a cassette are positioned in more accessible locations.For example, instead of a front to rear arrangement, some of theconnectors can be positioned on the side of the cassette to permitimproved technician access.

According to another aspect of the present invention, multiple flexiblefoils can be used with a single fiber connector wherein the foils areconnected to different sources, such as an Ethernet source, and a systemcontrol source.

A further aspect of the present invention relates to utilizing a 12multi-fiber connector having one or more rows of 12 fibers, and aflexible foil in combination with additional multi-fiber connectors. Inone embodiment, the fibers of multiple connectors are combined toconnect to a second connector. For example, from a 12 fiber 10 GigabitEthernet channel connector which uses twelve fibers can be connected toa 40 Gigabit Ethernet channel connector wherein only 8 fibers are used.In such an arrangement, 4 of the fibers, typically the middle 4 fibers,can be dark fibers, or can be utilized by connection to a differentsource. In such an arrangement, three 40 Gigabit Ethernet connectors canbe connected to two 10 Gigabit ethernet connectors, and the additionalfibers of the 40 Gigabit Ethernet connectors can be dark fibers, orconnected to an alternate source. In this example, eight fibers from afirst connector and four fibers from a second connector are routed onthe flexible foil to one connector, and eight fibers from a thirdconnector and four fibers from the second connector are routed toanother connector. The arrangement is a 3 to 2 connector cablearrangement, making use of twelve fiber connectors (or multiples of 12).

In the case of a 100 Gigabit Ethernet connector, two rows of 12 fibersin the connector can be provided wherein 10 pairs are utilized forsignal transmission. The outer fibers of each row are not utilized, andcan be dark fibers on the flexible foil, or can be connected to analternate source.

A variety of additional inventive aspects will be set forth in thedescription that follows. The inventive aspects can relate to individualfeatures and combinations of features. It is to be understood that boththe foregoing general description and the following detailed descriptionare exemplary and explanatory only and are not restrictive of the broadinventive concepts upon which the embodiments disclosed herein arebased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top, front, right side perspective view of a fiber opticcassette having features that are examples of inventive aspects inaccordance with the present disclosure;

FIG. 2 is a top, rear, right side perspective view of the fiber opticcassette of FIG. 1;

FIG. 3 is a top, front, left side perspective view of the fiber opticcassette of FIG. 1;

FIG. 4 is a top, rear, left side perspective view of the fiber opticcassette of FIG. 1;

FIG. 5 is a top plan view of the fiber optic cassette of FIG. 1;

FIG. 6 is a bottom plan view of the fiber optic cassette of FIG. 1;

FIG. 7 is a front elevational view of the fiber optic cassette of FIG.1;

FIG. 8 is a rear elevational view of the fiber optic cassette of FIG. 1;

FIG. 9 is a right side view of the fiber optic cassette of FIG. 1;

FIG. 10 is a left side view of the fiber optic cassette of FIG. 1;

FIG. 11 is a partially exploded perspective view of the fiber opticcassette of FIG. 1;

FIG. 12 is another partially exploded perspective view of the fiberoptic cassette of FIG. 1;

FIG. 13 is a fully exploded perspective view of the fiber optic cassetteof FIG. 1;

FIG. 14 is another top, front, right side perspective view of the fiberoptic cassette of FIG. 1;

FIG. 14A is a close-up view illustrating the ferrule assemblies of theflexible optical circuit placed within the body of the cassette of FIG.1;

FIG. 15 is a cross-sectional view taken along line 15-15 of FIG. 7;

FIG. 15A is a close-up view showing the internal features of one of theferrule assemblies of the flexible optical circuit placed within thecassette of FIG. 1;

FIG. 16 is a top, front, right side perspective view of the flexibleoptical circuit of the fiber optic cassette of FIG. 1;

FIG. 17 is a bottom, front, left side perspective view of the flexibleoptical circuit of FIG. 16;

FIG. 18 is a bottom plan view of the flexible optical circuit of FIG.16;

FIG. 19 is a front elevational view of the flexible optical circuit ofFIG. 16;

FIG. 20 is a left side view of the flexible optical circuit of FIG. 16;

FIG. 21 is a diagrammatic view illustrating a top cross-sectional viewof one of the ferrule assemblies of the flexible optical circuit placedwithin the cassette of FIG. 1, the cross-section taken by bisecting theferrule assembly along its longitudinal axis;

FIG. 22 is a diagrammatic view illustrating a side cross-sectional viewof the ferrule assembly of FIG. 21, the cross-section taken by bisectingthe ferrule assembly along its longitudinal axis;

FIG. 23 is a diagrammatic view illustrating the ferrule assembly of FIG.21 from the rear side;

FIG. 24 is a diagrammatic view illustrating a side view of one of thepigtails extending from the substrate of the flexible optical circuit tobe terminated to the ferrule assembly of FIG. 21;

FIG. 25 is a top, front, right side perspective view of a secondembodiment of a fiber optic cassette having features that are examplesof inventive aspects in accordance with the present disclosure, thefiber optic cassette shown in a fully-assembled configuration;

FIG. 26 is a partially exploded view of the fiber optic cassette of FIG.25 taken from a top, rear, right side perspective of the fiber opticcassette;

FIG. 27 is a fully exploded view of the fiber optic cassette of FIG. 25taken from a top, front, right side perspective of the fiber opticcassette;

FIG. 28 is a fully exploded right side view of the fiber optic cassetteof FIG. 25;

FIG. 29 is a partially assembled view of the fiber optic cassette ofFIG. 25 taken from a top, front, right side perspective of the fiberoptic cassette, wherein the cover has been removed to expose theinterior features of the fiber optic cassette;

FIG. 30 is a top plan view of the partially assembled fiber opticcassette of FIG. 29;

FIG. 31 is a right side view of the partially assembled fiber opticcassette of FIG. 29;

FIG. 32 is a bottom plan view of the cover of the fiber optic cassetteof FIG. 25;

FIG. 33 is a top, front, right side perspective view of the flexibleoptical circuit of the fiber optic cassette of FIG. 25;

FIG. 34 is a top plan view of the flexible optical circuit of FIG. 33;

FIG. 35 is a front elevational view of the flexible optical circuit ofFIG. 33;

FIG. 36 is a right side view of the flexible optical circuit of FIG. 33;

FIG. 37 is a top plan view of a flexible optical circuit illustrating asubstrate of the circuit with a bend formed therein;

FIG. 38 is a perspective view of the flexible optical circuit of FIG.37;

FIG. 39 is another perspective view of the flexible optical circuit ofFIG. 37;

FIG. 40 is a top, front, right side perspective view of a thirdembodiment of a fiber optic cassette having features that are examplesof inventive aspects in accordance with the present disclosure, thefiber optic cassette shown in a partially-assembled configurationwithout the cover thereof;

FIG. 41 is another top, front, right side perspective view of the fiberoptic cassette of FIG. 40;

FIG. 42 is a right side view of the fiber optic cassette of FIG. 40;

FIG. 43 illustrates a top, front, right side perspective view of aflexible optical circuit including a twist-bend in the substrate of thecircuit;

FIG. 44 is a top, front, left side perspective view of the flexibleoptical circuit of FIG. 43;

FIG. 45 is a top view of the flexible optical circuit of FIG. 43;

FIG. 46 is a perspective view of a multi-ferrule strip configured foruse with the fiber optic cassettes of the present disclosure, themulti-ferrule strip including a plurality of ferrule hubs integrallymolded together;

FIG. 47 is a top plan view of the multi-ferrule strip of FIG. 46;

FIG. 48 is a front elevational view of the multi-ferrule strip of FIG.46;

FIG. 49 is a left side view of the multi-ferrule strip of FIG. 46;

FIG. 50 is a cross-sectional view taken along line 50-50 of FIG. 48;

FIG. 51 is a perspective view of another embodiment of a flexibleoptical circuit including loops of buffered fiber between the substrateof the circuit and the ferrule assembly for repair/replacement;

FIG. 52 is a top plan view of the flexible optical circuit of FIG. 51;

FIG. 53 illustrates a perspective view of a plurality of duplex flexibleoptical circuits in an exploded configuration, the duplex flexibleoptical circuits configured to be placed within the fiber opticcassettes of the present disclosure in a stacked arrangement;

FIG. 54 illustrates a top, front, right side perspective view of theplurality of duplex flexible optical circuits of FIG. 53 in a stackedarrangement;

FIG. 54A is a close-up view illustrating the transition region of thestacked duplex flexible optical circuits of FIG. 54, wherein the fiberstransition from a stepped configuration of the stacked circuits to aribbonized flat section for termination to a multi-ferrule connector;

FIG. 55 illustrates a top, rear, left side perspective view of theplurality of duplex flexible optical circuits of FIG. 53 in a stackedarrangement;

FIG. 55A is a close-up view illustrating the transition region of thestacked duplex flexible optical circuits of FIG. 55, wherein the fiberstransition from a stepped configuration of the stacked circuits to aribbonized flat section for termination to a multi-ferrule connector;

FIG. 56 is a top, front, right side exploded perspective view of a clampstructure used for clamping the plurality of duplex flexible opticalcircuits of FIG. 53 in a stacked arrangement, the clamp structure shownwith the stack of the duplex flexible optical circuits placed therein;

FIG. 57 is a top, rear, left side exploded perspective view of the clampstructure of FIG. 56, the clamp structure shown with the stack of theduplex flexible optical circuits placed therein;

FIG. 57A is a close-up view illustrating the clamp structure of FIG. 57;

FIG. 58 is a right side exploded perspective view of the clamp structureof FIG. 56 and the plurality of duplex flexible optical circuits of FIG.53;

FIG. 59 is a rear exploded perspective view of the clamp structure ofFIG. 56 and the plurality of duplex flexible optical circuits of FIG.53;

FIG. 60 illustrates the clamp structure of FIG. 56 and the plurality ofduplex flexible optical circuits of FIG. 53 in a clamped arrangement;

FIG. 60A is a close-up view illustrating the clamp structure of FIG. 60;

FIG. 61 illustrates the upper and lower members of the clamp structureof FIG. 56; and

FIG. 62 is a top, rear, right side perspective view of a plurality ofduplex flexible optical circuits similar to those of FIGS. 53-55 in astacked arrangement, the duplex flexible optical circuits shown in anunterminated configuration;

FIG. 63 illustrates one of the duplex flexible optical circuits of FIG.62, wherein one of the pigtails is shown as terminated to a ferruleassembly and the other of the pigtails shown exploded off a ferruleassembly;

FIG. 64 illustrates a plurality of ferrule assemblies that have beenterminated to the pigtails of the flexible optical circuits of FIGS.62-63, wherein one of the terminated ferrule assemblies is shown in across-sectional view bisecting the ferrule assembly along itslongitudinal axis;

FIG. 65 is a cross-sectional view taken along line 65-65 of FIG. 64;

FIG. 66 is a cross-sectional view taken along line 66-66 of FIG. 64;

FIG. 67 is a top, rear, right side perspective view of anotherembodiment of a fiber optic cassette having features that are examplesof inventive aspects in accordance with the present disclosure, thefiber optic cassette configured to house the duplex flexible opticalcircuits shown in FIGS. 62-64, the fiber optic cassette shown in apartially exploded configuration;

FIG. 68 illustrates the fiber optic cassette of FIG. 67 with the ferruleassemblies of the flexible optical circuits removed from the pockets ofthe adapter block of the cassette;

FIG. 69 is a close-up view of a portion of the fiber optic cassette ofFIG. 68;

FIG. 70 illustrates the fiber optic cassette of FIG. 67 from a front,bottom, right side perspective view, the cassette shown in a partiallyexploded configuration;

FIG. 71 illustrates the fiber optic cassette of FIG. 68 from a rear,bottom, right side perspective view;

FIG. 72 is a close-up view of a portion of the fiber optic cassette ofFIG. 71; and

FIG. 73 illustrates a fiber optic connector making electrical contactwith media reading interfaces of the printed circuit board of thecassette of FIGS. 67-72;

FIG. 74 is a perspective view of a first embodiment of a flexible foilincluding dark fibers;

FIG. 75 is a top view of the flexible foil of FIG. 74;

FIG. 76 is an enlarged view of a portion of the flexible foil of FIG.74, showing the placement of the dark fibers;

FIG. 77 shows multiple foil layers connected to a multi-fiber connectorhaving multiple rows of fibers (all fibers live);

FIG. 78 shows multiple foil layers connected to a multi-fiber connectorwherein different rows of the fibers of the connector are connected todifferent foils;

FIG. 79 shows multiple foils connecting a single connector to twomulti-fiber connectors wherein each of the multi-fiber connectorsinclude inactive fibers which can be filled with dark fibers, orconnected to an alternate source;

FIG. 80 shows multiple foil layers connected to multi-fiber connectorswherein a side access is provided;

FIG. 81 shows a single foil including some fibers passing through from afront to a back, and some fibers looping back to the same connector, oranother connector;

FIG. 82 shows another single foil including some fibers passing throughfrom a front to back, and some fibers looping back to the same connectoror another connector;

FIG. 83 shows a multi-fiber connector connected to multiple foil layersconnected to different sources, an Ethernet source, and a system controlsource;

FIG. 84 shows an example flex foil using 12 fiber connectors in a 3 to 2arrangement, and including the use of dark fibers;

FIG. 85 shows a close up view of the transition from 2 twelve fiberssubstrates to 3 twelve fiber substrates.

DETAILED DESCRIPTION

The present disclosure is directed generally to fiber optic devices inthe form of fiber optic cassettes. As will be described in furtherdetail below, the different embodiments of the fiber optic cassettes ofthe present disclosure are designed to relay multiple fibers whichterminate at a rear connector, such as an MPO style connector, to aplurality of ferrules positioned at a generally front portion of thecassette. The fiber optic cassettes of the present disclosure, thus,provide a transition housing or support between multi-fiberedconnectors, such as the MPO style connectors having MT ferrules, andsingle or dual fiber connectors, such as LC or SC type connectors.

As will be described in further detail below, the different embodimentsof the fiber optic cassettes of the present disclosure utilize flexibleoptical circuits for the transition between the multi-fibered connectorspositioned at one end of the cassette and the single or dual connectorspositioned at an opposite end of the cassette.

Flexible optical circuits are passive optical components that compriseone or more (typically, multiple) optical fibers imbedded on a flexiblesubstrate, such as a Mylar™ or other flexible polymer substrate.Commonly, although not necessarily, one end-face of each fiber isdisposed adjacent one longitudinal end of the flexible optical circuitsubstrate and the other end face of each fiber is disposed adjacent theopposite longitudinal end of the flexible optical circuit substrate. Thefibers extend past the longitudinal ends of the flexible optical circuit(commonly referred to as pigtails) so that they can be terminated tooptical connectors, which can be coupled to fiber optic cables or otherfiber optic components through mating optical connectors.

Flexible optical circuits essentially comprise one or more fiberssandwiched between two flexible sheets of material, such as Mylar™ oranother polymer. An epoxy may be included between the two sheets inorder to adhere them together. Alternately, depending on the sheetmaterial and other factors, the two sheets may be heated above theirmelting point to heat-weld them together with the fibers embeddedbetween the two sheets.

The use of flexible optical circuits within the fiber optic cassettes ofthe present disclosure provides a number of advantages, which will bediscussed in further detail below. For example, the substrate of aflexible optical circuit is mechanically flexible, being able toaccommodate tolerance variations in different cassettes, such as betweenconnector ferrules and the housings that form the cassettes. Theflexibility of the optical circuits also allow for axial movement in thefibers to account for ferrule interface variation. Also, by providing arigid substrate within which the fibers are positionally fixed, use offlexible optical circuits allows a designer to optimize the fiber bendradius limits and requirements in configuring the cassettes, thus,achieving reduced dimensions of the cassettes. The bend radius of thefibers can thus be controlled to a minimum diameter. By utilizingoptical fibers such as bend insensitive fibers (e.g., 8 mm bend radius)in combination with a flexible substrate that fixes the fibers in agiven orientation, allowing for controlled bending, small form cassettesmay be produced in a predictable and automated manner. Manual handlingand positioning of the fibers within the cassettes may be reduced andeliminated through the use of flexible optical circuits.

Now referring to FIGS. 1-24, a first embodiment of a fiber opticcassette 10 that utilizes a flexible optical circuit 12 is shown. In thefiber optic cassette 10 of FIGS. 1-24, the flexible optical circuit 12is depicted as transitioning optical fibers 14 between a conventionalconnector 16 (e.g., an MPO connector) at the rear 18 of the cassette 10and a plurality of non-conventional connectors 20 at the opposite frontend 22 of the cassette 10, wherein portions of a substrate 24 of theflexible optical circuit 12 are physically inserted into thenon-conventional connectors 20.

It should be noted that the term “non-conventional connector” may referto a fiber optic connector that is not of a conventional type such as anLC or SC connector and one that has generally not become a recognizablestandard footprint for fiber optic connectivity in the industry.

The elimination of conventional mating connectors inside the cassette 10may significantly reduce the overall cost by eliminating the skilledlabor normally associated with terminating an optical fiber to aconnector, including polishing the end face of the fiber and epoxyingthe fiber into the connector. It further allows the fiber opticinterconnect device such as the optical cassette 10 to be made verythin.

Still referring to FIGS. 1-24, the cassette 10 includes a body 26defining the front 22, the rear 18 and an interior 28. Body 26 furtherincludes a top 30, a bottom 32, and sides 34, 36.

A signal entry location 38 may be provided by the MPO connector 16,which in the illustrated embodiment is along the rear 18 of the cassettebody 26. A pocket 40 seats the MPO connector 16 while flexiblecantilever arms 42 may be provided for coupling a second mating MPOconnector to the cassette 10 with a snap-fit interlock. Non-conventionalconnectors 20 are arranged linearly adjacent the front 22 of thecassette 10 and positioned along a longitudinal axis A defined by thebody 26. In the depicted embodiment of the cassette 10, the MPOconnector 16 of the cassette 10 is positioned to extend parallel to thelongitudinal axis A and generally perpendicular to ferrules 44 of thenon-conventional connectors 20 at the front 22 of the cassette 10.

In general, cassette 10 includes the top 30 and bottom 32 which aregenerally parallel to each other and define the major surfaces ofcassette body 26. Sides 34, 36, front 22, and rear 18 generally definethe minor sides of cassette body 26. The cassette 10 can be oriented inany position, so that the top and bottom surfaces can be reversed, orpositioned vertically, or at some other orientation.

In the embodiment of the fiber optic cassette 10 shown in FIGS. 1-24,the non-conventional connectors 20 that are positioned adjacent thefront 22 of the cassette 10 each defines a hub 46 mounted over theferrule 44. A cross-section of the interface is seen in FIGS. 15 and15A. Each ferrule 44 is configured to terminate one of the fibers 14extending out from the flexible circuit 12, as shown in FIGS. 21-24.

The non-conventional connectors 20 are placed within pockets 48 providedat a connection block or array 50 located at the front 22 of thecassette 10. A split sleeve 52 is also provided for ferrule alignmentbetween the hub 46 and ferrule 44 of each non-conventional connector 20and the ferrule of another mating connector that enters the cassette 10from the front 22.

The mating connectors entering the cassette 10 from the front 22 of thecassette 10 may be connected through fiber optic adapters that aremounted on the connection block 50. The cassette 10 of FIGS. 1-24 isshown without the rows of adapters at the front 22 of the cassette 10that would allow conventional connectors such as LC connectors to bemated to the non-conventional connectors 20 located within the interior28 of the cassette 10. Such adapters or adapter blocks may be snap-fit,ultrasonically welded, or otherwise attached to the rest of the cassettebody 26. In the versions of the fiber optic cassettes 110, 210illustrated in FIGS. 25-36 and 40-42, respectively, the rows of fiberoptic adapters 5 are shown on the cassettes 110, 210.

In the illustrated embodiment of the cassette 10 of FIGS. 1-24, theadapters that would be used with the cassette 10 are sized to receivemating LC connectors. SC connectors can also be used with appropriatesized adapters.

The cassette 10 of FIGS. 1-24 can be sealed or can be openable, so as toallow repair, or cleaning of the inner hubs 46 and ferrules 44. In somecases, the adapter blocks can be snap fit to a rest of the body 26 forease of assembly. Adapter blocks can also preferably be removed from arest of the cassette 10 to allow for cleaning of the innernon-conventional connector 20. The flexible fiber optic circuit 12allows the entire fiber bundle, including the MPO connector 16 to beable to be removed for cleaning or replacement.

Referring specifically now to FIGS. 13 and 16-24, fiber pigtails 14extending out from a rear end 54 of the substrate 24 forming theflexible optical circuit 12 are ribbonized for termination to an MTferrule 56 of the MPO connector 16. The fiber pigtails 14 extending outfrom a front end 58 of the substrate 24 are individually terminated tothe ferrules 44 to be positioned at the front 22 of the cassette 10. Asshown, the substrate 24 defines front extensions 60 (one per fiber 14)each provided in a spaced apart configuration for providing someflexibility to the substrate 24. The individual fibers 14 are separatedout from the ribbonized section at the rear 54 of the substrate 24 andare routed through the substrate 24 to the individual front extensions60. Each ferrule hub 46 defines a notch or a cut-out 62 for receivingfront portions 64 of the front extensions 60 of the substrate 24.

Fiber pigtails 14 that extend from each of the front extensions 60 ofthe substrate 24 are illustrated in FIGS. 21-24 diagrammatically.Referring now to the diagrammatic views of FIGS. 21-24, according to oneexample embodiment, the fiber pigtails 14 extending from the substrate24 may be defined by an optical fiber 66 that is made up of a fiber coresurrounded by a cladding layer. A portion 68 of the front extension 60of the substrate 24 forming the flexible optical circuit 12 is insertedinto a cylindrical bore 70 extending through the center of the ferrulehub 46, while an exposed optical fiber 66 that is made up of the fibercore and the surrounding cladding (after the primary coating has beenstripped) is inserted into the ferrule 44 (see FIG. 21). The cut-out 62of the ferrule hub 46 receives the portion 68 of the front extension 60of the substrate 24 in stabilizing the termination.

According to one example process step, by using a rigid substrate, whenthe fibers are being terminated to the ferrules 44, the ends of thefibers may be cleaved and ends of all of the ferrules 44 extending fromthe substrate 24 may be polished simultaneously.

As shown in FIGS. 11-13, 15, and 15A, in addition to the inherentability of the substrate 24 of the flexible optical circuit 12 toprovide a bias for the ferrules 44 of the non-conventional connectors 20at the front 22 of the cassette 10 for ferrule interface variations,other structures may be used to supplement the inherent bias of theflexible circuit 12. For example, in the depicted embodiment of thecassette 10, a spring clip 72 is positioned within a pocket 74 in thecassette 10 and extends parallel to the longitudinal axis A of thecassette body 26. In a conventional fiber optic connector, the ferrulesassemblies normally include springs such that when they are mated in anadapter, the ferrules are pressed together against the bias of thespring. In the depicted cassette 10, the spring clip 72 may bepositioned to abut rear ends 75 of the ferrule hubs 46 so as providesome bias to the ferrules 44 when they are mating incoming connectors.The flexibility of the substrate 24 of the flexible optical circuit 12allows the ferrules 44 of the non-conventional connectors 20 to flexback and the spring clip 72 provides additional bias to force themforwardly. The spring clip 72 may be adhered to the portions of thecassette 10 for rigidly fixing the spring clip 72 within the cassette10.

It should be noted that a structure such as the spring clip 72 can beused on any of the embodiments of the fiber optic cassettes describedand illustrated in the present application.

Referring now to FIGS. 25-36, another embodiment of a fiber opticcassette 110 is illustrated. The fiber optic cassette 110, similar tothe cassette 10 of FIGS. 1-24, utilizes a flexible fiber optic circuit112 within the body 126 for relaying fibers 114. In this embodiment, amulti-fiber connector 116 (in the form of an MPO connector) is orientedparallel to non-conventional connectors 120 that are at the front 122 ofthe cassette 110, generally perpendicular to the longitudinal axis Adefined by the cassette 110. The multi-fiber connector 116 is mounted tothe cassette 110 via a multi-fiber adapter 111 seated within a pocket140 at a rear 118 of the cassette 110.

The flexible circuit 112 is configured to transition fibers 114 from themulti-fiber connector 116 at the rear 118 defining the signal entrylocation 138 to non-conventional connectors 120 at the front 122 of thecassette 110. The cassette 110 is shown to include multiple rows ofadapters 5 in the form of an adapter block 115 at the front 122 of thecassette 110. Via the adapters 5, conventional connectors such as LCconnectors may be mated with ferrules 144 of the non-conventionalconnectors 120 located at the front 122 of the cassette 110. Theadapters 5 are arranged linearly and positioned along longitudinal axisA. In the illustrated embodiment, adapters 5 are sized to receive frontLC connectors. SC connectors can also be used with appropriate sizedadapters. In the illustrated embodiment, the adapters 5 are formed in ablock construction 115 having a front end 117, and an opposite rear end119. Front end 115 includes a profile for receiving LC connectors. Atthe rear end 119 of the adapter block 115, the ferrule assemblies of thenon-conventional connectors 120 including the ferrule hubs 146 and theferrules 144 are seated in pockets 148 aligned with ports 121 of theadapters 5. For each connector pair, a split sleeve 152 is also providedfor ferrule alignment between hub and ferrule of each non-conventionalconnector 120 and the ferrule of a conventional LC connector.

As shown and as discussed previously, the adapter blocks 115 may be snapfit, ultrasonically welded or otherwise attached to a rest of thecassette body 126 or formed as part of the body 126. A cover 127 may beused to cover an area behind blocks 115. In FIGS. 26-31, the cassette110 has been shown with the cover 127 removed or without the cover 127to illustrate the internal features of the cassette 110.

As in the first embodiment of the cassette 10, the cassette 110 of FIGS.25-36 is configured such that it can be sealed or can be openable, so asto allow repair, or cleaning of the inner hub 146 and ferrule 144. Insome cases, the adapter blocks 115 can be snap fit to a rest of the body126 for ease of assembly. Adapter blocks 115 can also preferably beremoved from a rest of the cassette 110 to allow for cleaning of theinner non-conventional connector 120. The flexible fiber optic circuit112 allows the entire fiber bundle, including the MPO connector 116 tobe able to be removed for cleaning or replacement.

The termination of the fiber pigtails 114 extending from a front 158 ofthe substrate 124 of the flexible circuit 112 is similar to thetermination for the ferrule assemblies described above with respect tothe cassette 10 of FIGS. 1-24. At the rear 154 of the substrate 124, asdescribed previously, the fibers 114 are ribbonized for termination toan MT ferrule 156.

The substrate 124 includes extensions 160 at the front side 158. Theextensions 160 define cut-outs 161 between each one. The cutouts 161allow flexibility for the substrate 124 and essentially enable theferrules 144 of the non-conventional connectors 120 to be generally freefloating structures to allow for movement in two different axes (e.g.,upward/downward, front/back).

Referring specifically to FIGS. 27, 28, 31, 33, and 36, the substrate124 of the flexible optical circuit 112 is also illustrated with a bentportion 125 adjacent the rear pocket 140 of the cassette 110. Asdiscussed previously, one advantage of using a flexible substrate 124 toanchor the fibers 114 is to allow limited controlled movement of thesubstrate 124 either to accommodate any tolerance variances between theinternal components and the cassette body 126 or to accommodate anymovement of the internal ferrules 144 during connection to incomingconnectors.

An example of a simple flexible optical circuit 312 having a substrate324 that includes a design for controlled bending and allowing axialmovement in the fibers 314 is illustrated in FIGS. 37-39. Either aU-bend or an S-bend 325 can be provided in the substrate 324 of theflexible optical circuit 312 for allowing axial movement for the fibers314. With the tolerances of connector ferrules and molded polymericstructures (such as the cassette body), there can be a significant buildup of ferrule interface variation. By allowing the substrate 324 of theflexible circuit 312 to bend in a controlled way, these tolerances canbe accommodated.

FIGS. 40-42 illustrate another embodiment of a fiber optic cassette 210utilizing a flexible optical circuit 212, wherein the bend 225 isprovided generally in the middle portion 227 of the substrate 224 of thecircuit 212. The substrate 224 of the cassette 210 of FIGS. 40-42provides similar advantages as the cassettes 10, 210 described inprevious embodiments.

As another example, FIGS. 43-45 illustrate a flexible circuit 412including a substrate 424 with a twist 425 in the ribbonized-fiber partof the substrate 424. Such a design can accommodate a large distance invariation between connector interfaces. As shown in the embodiment ofthe flexible circuit 412 of FIGS. 43-45, the MPO connector at the rearend of the substrate may define a longitudinal axis that isperpendicular to those of the non-conventional connectors at the frontof the substrate 424. Thus, the fibers 14 extending from the MPOconnector may follow an “S” or “Z” shaped pathway before beingterminated to the front connectors. In the depicted embodiment, theoptical fibers 14 enter the substrate 424 in a side-by-side,non-overlapping configuration and branch out therefrom as they extend tothe non-conventional connectors at the front of the substrate. Thesubstrate 424 allows the fibers 14 to follow such a path whilepreserving any minimum bend radius requirements. In a different exampleembodiment that will be discussed below shown in FIGS. 51, 52, thefibers entering the substrate at the back may be oriented parallel tothe portions exiting from the front of the substrate. In such anexample, the fibers may enter from the rear of the substrate, again, ina non-overlapping configuration and may branch out to the differentnon-conventional connectors at the front of the substrate, followingminimum bend radius requirements.

Referring now to FIGS. 46-50, an embodiment of a ferrule strip 500 isillustrated. One of the issues normally encountered in assembly of thecassettes (e.g., 10, 110, 210) utilizing non-conventional connectors(e.g., 20, 120) at one end of the adapter blocks (e.g., 115) is theloading of the ferrule hubs (e.g., 46, 146) onto the flex circuit (e.g.,12, 112, 212) and handling of the ferrule hubs. According to oneinventive method, the ferrules (e.g., 44, 144) may be overmolded with apolymeric multi-ferrule strip 500 that forms a plurality of integralhubs 546. The multi-ferrule strip 500 can be molded to hold the ferrules544 at the correct pitch for insertion into the pockets (e.g., 48, 148)of the cassettes (e.g., 10, 110, 210).

Now referring generally to FIGS. 51-61, when using a flexible circuitthat includes a plurality of fibers embedded therein, production yieldmay be a big issue, especially given that all of the individual fibershave to be separately terminated into individual ferrules at the frontof the flexible optical circuit. If there is any damage to one of theterminations (e.g., either to a fiber or to a ceramic ferrule), theentire flexible circuit may become unusable. The present disclosurecontemplates methodologies for allowing individual retermination of thefibers if one of the optical fibers or ferrules fails.

Referring specifically now to FIGS. 51-52, according to one embodimentmethodology, a looped length 613 of buffered fiber 614 may be storedwithin the cassette between the flexible substrate 624 and each of thenon-conventional connectors 620. If one of the terminations fails, atechnician would be able to unloop the length 613 of fiber 614 andreterminate, saving the rest of the flexible circuit 612.

According to another methodology, as illustrated in FIGS. 53-61, insteadof utilizing a single flexible substrate for all of the fibers relayedfrom the multi-fiber connector 716, a plurality of separate duplexsubstrates 724 can be used in a stacked arrangement. Each duplex stackcan be mounted removably on the cassette and may be removed for repairor replacement if one of the terminations fails.

As shown in FIGS. 53-61, according to one embodiment, there may be sixduplex flex circuits 712 including six substrates 724, totaling thetwelve fibers 714 coming from an MPO connector. In such an embodiment,all six of the substrates 724 may be provided by, for example,manufacturing three different shapes and then flipping the threedifferently shaped substrates 180 degrees to provide the six neededduplex substrates 724 for the whole stack. As shown in FIGS. 53-55, thethree different shapes would be configured such that, when stacked,front extensions 760 of the substrates 724 would be spaced apart toresemble the front extensions (e.g., 60, 160) of a single integralsubstrate (e.g., 24, 124, 224) and to fit within the internalconfiguration of a given cassette.

Referring now to FIGS. 54, 54A, 55, 55A, 56, 57, 57A, 58-60, 60A, and61, since the portion of the fibers 714 that are to be terminated to theMT ferrule of an MPO connector have to be provided in a flat, ribbonizedconfiguration for the termination and since the stacked flex circuits712 have the fibers 714 in a stepped configuration, a clamp structure780 that acts as a fiber transition device may be used within thecassette 712.

As shown in FIGS. 54, 54, 54A, 55, 55A, 56, 57, 57A, 58-60, 60A, and 61,the clamp structure 780 may include an upper member 782 that is snap fitto a lower member 784 with cantilever arms 786 that have tapered tabs788. Both the upper and the lower members 782, 784 of the clampstructure 780 provide a fiber channel/guide 790 that includes steps 792for transitioning the fibers 714 from a stepped configuration to a flatconfiguration for terminating to the MT ferrule 756 of an MPO connector716. The clamp 780 is designed such that stacked flex fibers 714 areconverted to a linear plane so they can be ribbonized while maintainingthe minimum bend radius requirements of the fibers 714. The upper andlower members 782, 784 of the clamp structure 780 removably snaptogether for both holding the stacked substrates 724 in position and forcontrolling the transition of the fibers 714 while supporting bendradius limitations. If any of the flex substrates, the ferrules, or thefibers is damaged, the clamp structure 780 can be taken apart, removingthe flex substrate 724 to be repaired or replaced.

According to certain embodiments, any of the cassettes described aboveand illustrated herein may have a length of 3 to 4 inches (parallel tothe longitudinal direction A), a width of 2 to 3 inches (front to back),and a height of approximately ½ inch. More preferably, the length may be3 to 3½ inches, the width may be 2 to 2½ inches, and the height may be ½inch. The height can vary as needed, such as to accommodate differentformats of adapters 5 or multiple rows of adapters 5.

Referring now to FIGS. 62-66, another example method for terminating afiber pigtail 814 extending out from a front end 858 of a flex substrate824 to a ferrule of a non-conventional connector is illustrated. In thedepicted embodiment, duplex flex circuits 812 similar to flex circuits712 discussed above are used to illustrate the example terminationmethod. As shown in FIG. 62, such duplex circuits 812 are provided in astacked arrangement when being placed into a cassette body. According tothe embodiment shown in FIGS. 62-66, the pigtails 814 that are to beindividually terminated to ferrules 844 are formed by stripping aportion of the flex substrate 824 (including a primary coating layer ofthe fiber) such that an optical fiber 866 formed from a combination of afiber core and a cladding layer is left. In certain embodiments, theoptical fiber 866 formed from the fiber core and the cladding layer maybe 125 micron in cross-dimension. The primary coating layer that isstripped is generally around 250 micron in cross-dimension according toone embodiment. The optical fiber 866 extends from a portion 868 of afront extension 860 of the flex substrate 824 that is to be insertedinto the ferrule hub 846. According to certain embodiments, portion 868defines a generally square cross-sectional shape having side dimensionsof 0.5 mm each. Thus, the square cross-sectional portion 868 is able tobe inserted into a cylindrical bore 870 extending through the center ofa ferrule hub 846, which may be about 0.9 mm in diameter (see FIGS.63-66). The exposed optical fiber 866 that is made up of the fiber coreand the surrounding cladding (after the primary coating has beenstripped) is inserted into the ferrule 844, as seen in FIGS. 64-66.

Now referring to FIGS. 67-73, an example of a cassette 810 that isconfigured for receiving stacked flex circuits such as the flex circuits812 shown in FIGS. 62-66 is illustrated. The cassette 810 is similar incertain aspects to the cassettes 10, 110, and 210 shown in previousembodiments. However, the cassette 810 defines pockets 848 at the frontend 822 of the cassette body that match the exterior shape of theferrule hubs 846 (e.g., having hexagonal footprints), wherein thepockets 848 are configured to fully surround the ferrule hubs 846. Thepockets 848 are formed from portions of the cassette body that areintegrally formed with the adapter block 815 of the cassette 810. Asshown, the adapter block 815 is removably inserted into the cassettebody 826. The pockets 848, also having a hexagonal configuration, matchthe exterior shape of the ferrule hubs 846 and prevent rotation of thehubs therewithin. In this manner, the hubs are retained in a stablemanner during termination, assembly, polishing, etc.

Even though the ferrule hubs 846 and the matching pockets 848 have beenillustrated with a hexagonal cross-section in the depicted embodiment,in other embodiments, the keying mechanism can be provided usingdifferent cross-sectional shapes having flat portions (such as square,rectangular, etc.). For example, an embodiment of a ferrule usable withthe cassettes of the present disclosure having squared ferrule hubs hasbeen shown in FIGS. 53-57 and 60.

As shown, the cassette body 826 defines pockets 840 for receiving aclamp structure 880 (similar to the clamp structure 780 of FIGS. 56-61)and an MPO connector 816 that is terminated to the rear ends of theindividual duplex flex substrates 824.

Still referring to FIGS. 67-73, the embodiment of the cassette 810 usedwith the stacked duplex flex circuits 812 has been illustrated withfurther additional aspect that may be used on the cassettes (e.g., 10,110, 210) of the earlier embodiments. For example, in accordance withsome aspects, certain types of adapters that form the adapter blocks atthe fronts of the cassettes may be configured to collect physical layerinformation from one or more fiber optic connectors (e.g., LCconnectors) received thereat. Certain types of adapters may include abody configured to hold one or more media reading interfaces that areconfigured to engage memory contacts on the fiber optic connectors. Theone or more media reading interfaces may be positioned in each adapterbody in different ways. In certain implementations, the adapter body maydefine slots extending between an exterior of the adapter body and aninternal passage in which the ferrules of the connectors are received.Certain types of media reading interfaces may include one or morecontact members that are positioned in such slots. A portion of eachcontact member may extend into a respective one of the passages toengage memory contacts on a fiber optic connector.

In the depicted example of the cassette 810 of FIGS. 67-73, the contacts801 that extend into each of the adapter passages of the block 815 areon a removable structure. The contacts 801 are defined on a printedcircuit board 803 that is placed between the flexible circuits 812 andthe cover 827 of the cassette 810. The contacts 801 align with the topsides of the adapter passages and extend into the adapter passages so asto engage memory contacts of fiber optic connectors inserted into theadapter passages. The printed circuit board 803 is designed to relay theelectrical signals from the contacts 801 at the front of the cassette810 to the rear of the cassette 810 as shown in FIGS. 67-73. Aconductive path may be defined by the printed circuit board 803 betweenthe contacts 801 of the adapters at the front end with a master circuitboard. The master circuit board may include or connect (e.g., over anetwork) to a processing unit that is configured to manage physicallayer information obtained by the media reading interfaces. FIG. 73illustrates a fiber optic connector making electrical contact with themedia reading interfaces 801 of the printed circuit board 803 of thecassette 810.

Example adapters having media reading interfaces and example fiber opticconnectors having suitable memory storage and memory contacts are shownin U.S. Patent Publication No. 2011/0262077, the disclosure of which ishereby incorporated herein by reference.

In addition to the various uses and applications of the describedcassettes, the cassettes can be used to terminate the fibers of amulti-fiber FOT cable, such as a 144-fiber cable, to make installationof the terminated cables easier and faster.

One advantage of the disclosed cassettes is that handling in the fieldof individual connectors, MPO connectors, or fanouts with upjackets areeliminated. The dimensions of the cassettes 10, 110, 210, 810 may bereduced by using flexible substrates (e.g., 24, 124, 224, 824) thatallow optimization of the bend radius limits of the fibers by fixing thefibers in a given footprint or pattern. Also, manual handling andtermination of individual fibers within the cassettes is reduced oreliminated, wherein automated, repeatable terminations may be providedwithin the cassettes.

The cassettes described and illustrated herein may be used by beingmounted to different types of telecommunications fixtures. The cassettesof the present disclosure may be fixedly mounted or mounted, forexample, as part of slidably movable modules or packs.

Although in the foregoing description, terms such as “top”, “bottom”,“front”, “back”, “right”, “left”, “upper”, and “lower were used for easeof description and illustration, no restriction is intended by such useof the terms. The telecommunications devices described herein can beused in any orientation, depending upon the desired application.

Having described the preferred aspects and embodiments of the presentdisclosure, modifications and equivalents of the disclosed concepts mayreadily occur to one skilled in the art. However, it is intended thatsuch modifications and equivalents be included within the scope of theclaims which are appended hereto.

The above examples include flexible optical circuits connecting amulti-fiber (MPO) connector to individual fiber connectors. FIGS. 74-85show various examples of multi-fiber connector (MPO) to multi-fiberconnector (MPO) connections with a flexible optical circuit.

Twelve fiber connectors are known (including a single row or multiplerows of twelve fibers (for example, 2-6 rows)). Some examples use thetwelve fiber connectors, but not all fibers are signal/light carrying.These fibers are dark or unused but still part of the flexible foil.Such a construction enables ease of assembly by connecting all twelve(or multiples of twelve) fibers at the same time. If the unused fiberswere not present, there is a chance the multi-fiber ferrule could becomedamaged during polishing if open bores were present through the ferrule.

Multiple layers of flexible foil can be used as desired with one or moremulti-fiber connectors to improve ease of assembly and fiber management.

FIGS. 74-85 show various examples of flexible foils and multi-fiberconnectors. The foils can be housed in cassettes where the connectorsare connected to adapters as part of the cassettes. The foils can beused in other equipment without being housed in a cassette.

The foils are easier to handle during assembly since the fibers arehandled as a group (or subgroup). To terminate to a connector 16, thesubstrate is removed as is the fiber coating, then the glass fibers areconnected to the ferrule of the multi-fiber connector 16 in atraditional manner, such as with epoxy.

Referring to FIGS. 74-76, the flex foil is shown with multipleconnectors 16 connected to various fibers organized and supported by thefoil. In the example shown, not all of the fibers provided carrysignals. Specifically, on the side of the foil with three connectors 16,only eight of the twelve fibers carry signals, and the middle four, aredark fibers.

Referring now to FIGS. 77-83, various examples of foils and connectorsare shown with different routings. In some cases, the fibers areinactive, or dark. In some applications, these fibers can be used forcarrying other signals.

In FIG. 77, foil variants are shown where the connector rows terminateto different foils. A top row terminates to a top foil, and a bottom rowterminates to a bottom foil. The foils could have different origins.

In FIG. 78, foil variants are shown where the connector rows terminateto different foils. A row is shared between foils. There could be morethan two foils.

In FIG. 79, foil variants are shown where the connector rows terminateto different foils. The mating plug can be selectively loaded.

In FIG. 80, foil variants are shown where the fibers are distributedbetween connectors not parallel to each other, such as when externalaccess is restricted.

In FIG. 81, foil variants are shown where some fibers are passedthrough, and other fibers are looped back to the top row and out of theplug. Fibers come in on the bottom row. For example, eight fibers arelooped out, and four fibers are passed to far end, used for instance todrop a subset of fibers of a larger fiber count trunk to an individualcabinet or device, maybe in a daisy-chain fashion down a cabinet row.

In FIG. 82, foil variants are shown where some fibers are passedthrough, and other fibers are looped back to the top row and out of theplug. Fibers come in on the bottom row. For example, eight fibers arelooped out, and four fibers are passed to an individual cabinet ordevice.

In FIG. 83, foil variants are shown where the connector rows terminateto different foils. In this case, there can be mixing a 40 Gig Ethernetchannel and four control fibers from different sources, or fibers thatcan be used to test continuity of a channel, discover where the far endgoes, give visual illumination of a desired connector end using coloredlight to speed location of a connector in a panel or warn a user if thewrong connector is unplugged.

Referring now to FIGS. 84 and 85, a further embodiment of the cablearrangement of FIGS. 74-76 is shown wherein twelve fiber connectors 16are used at each end of the cable assembly, and each connector isterminated with twelve fibers. However, for the cable assembly end withthree connectors, each connector has four dark fibers. As shown, the endof the cable assembly with two connectors shares fibers from twodifferent connectors from the end with the three connectors. See alsoFIGS. 74-76.

It is to be appreciated that there could be branching devices such asoptical couplers or WDMs (Wavelength Division Multiplexers) within theflex circuit. This enables signal distribution and/or monitoring ofcircuits for presence of signal, and signal quality, for example.

1-3. (canceled)
 4. A fiber optic circuit comprising: a flexible opticalcircuit including a substrate and a plurality of coated fiber opticcables supported by the substrate; wherein the fiber optic cablesinclude a first plurality that connect between two multi-fiberconnectors, and a second plurality that only connect to one multi-fiberconnector and are dark fibers. 5-8. (canceled)